A college friend of Ross Ulbricht, the creator of the Silk Road online exchange, testified on Thursday that he helped Ulbricht troubleshoot the site in its early days, providing more ammunition for federal prosecutors to make the case Ulbricht was the mastermind behind the notorious illegal goods marketplace.

The testimony from Richard Bates could help federal prosecutors establish a timeline showing Ulbricht was heavily involved with the site beyond just creating it.

Ulbricht has admitted to creating the Silk Road site in early 2011. According to prosecutors, it would be used to facilitate the exchange of $1.2 billion in illegal goods, mostly drugs. Ulbricht’s defense lawyer, Joshua Dratel, argues that Ulbricht started the site only as “an experiment” and handed off the site to other operators shortly after he started it. He rejoined immediately prior to his arrest, lured back in by the new operators to serve as a fall guy, according to Dratel.

Prosecutors need to convince the jury that Ulbricht was involved in Silk Road through much of its existence.

Bates’ testimony—given in exchange for immunity from prosecution in technically abetting Silk Road—could help prosecutors in that it established that Ulbricht was involved in the site at least through the summer of 2011, after its usage started to grow dramatically.

Bates testified that he met Ulbricht while both were in college at University of Texas at Dallas. Bates and Ulbricht rekindled the friendship in 2010 when Bates moved to Austin, where Ulbricht lived at the time.

Through the end of 2010, Ulbricht had asked Bates, a software engineer, many questions about programming. When Bates asked why Ulbricht needed this information, he said it was for a “top secret project.” Over time, the questions became more technical, and in February of 2011 Bates, afraid Ulbricht was hacking Web servers, issued Ulbricht an ultimatum: reveal the project or no more answers would be forthcoming.

It was then Ulbricht disclosed the existence of Silk Road, and what he did. He asked Bates to keep it a secret from everyone that it was run by Ulbricht. “You gotta keep my secret, buddy,” Ulbricht wrote to Bates on Google Chat.

Bates would continue to periodically aid Ulbricht for the following few months, mostly over Google Chat. In March, Bates helped Ulbricht troubleshoot the site when the database stopped working from too many open connections. Ulbricht also shared with Bates his successes with the site, boasting about the media coverage the site had gotten.

Bates’ testimony will continue through Thursday, and he will be cross-examined by Dratel.

Dratel has shown himself to be aggressive in cross-examination, working to plant doubts among jury members about conclusions that can be drawn from the prosecution’s evidence.

Earlier Thursday, Dratel was reprimanded by District Judge Katherine Forrest when questioning the previous witness, FBI computer forensic scientist Thomas Kiernan, for going outside the acceptable scope of questions that can be asked in cross-examination.

Kiernan had testified about what he had found on Ulbricht’s laptop at the time of Ulbricht’s arrest. The laptop included a copy of the Silk Road website, including a number of PHP scripting files.

At one point, Dratel asked Kiernan about what a particular piece of PHP code did. At this point, Forrest immediately called a jury break, and sharply told Dratel that he could only question Kiernan about how he had retrieved the files and what he found on the files. He could not use Kiernan as his own computer expert, she said. Dratel argued that Kiernan was called as a witness because Kiernan had examined the contents of the machine, so asking about the source code of a Silk Road PHP file on that machine was fair game.

Texas resident Ulbricht was indicted last February, after being arrested in October 2013 in California. At the time of his arrest, Ulbricht was charged with narcotics conspiracy, engaging in a continuing criminal enterprise, conspiracy to commit computer hacking, and money laundering. Both the charges of narcotics and engaging in a criminal enterprise have maximum penalties of lifetime imprisonment.

The case is being tried at the U.S. District Court of the Southern District of New York.

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